Oil-switch.



R. TED-GER.

OIL SWITCH.

APPLICATION FILED OCT. 11. 1912.

1,180,805. Patented Apr. 25,1916.

M/YTNES'SES; 12v YEN TOR aA/ 4 HTUHAHZ? TH fiE-AELH y, m :4. W

/, ATTORNEY.

RICHARD TROGER, OF CHARLOTTENBURG, GERMANY, ASSIGNOR '10 GENERALELECTRIC COMPANY, A CORPORATION OI NEW YORK.

OIL-SWITCH.

specification.

My invention relates to electric switches,

. and particularly to oil switches for con- 'tacts of trolling circuitscarrying large amounts of energy. q

Experience has shown that when the cona switch are separated under oil,the are produced exerts an explosive effect and tends to throw the oilout of the switch, particularly if a large amount of current is flowingin the circuit when the contacts separate. Efforts have been made toprevent these explosions by strengthening the oil tank, or by inclosingthe contacts in an insulated casing or chamber strong enough to resistthe explosive action of the arc and protect the main body of the oilfrom the explosive action of the arc. In some types of switches, bafiiesor perforated plates have been mounted near the fixed contacts to dampenthe movement of the oil and keep it as near the contacts as possible.All of these expedients deal only with the explosive action of the arcitself. Experience has shown, however, that the explosive action of thearc is not the only reason for explosions in oil switches, but thatexplosions occur in cases where the arc is confined in various ways andwhere there has been no direct discharge between the contacts at thesurface of the oil. Such explosions appear to be caused by the formationof bubbles of vapor of very high temperature in the im- These bubblesmediate-vicinity of the arc. of vapor tend'to rise through the oil andare still at a very high temperature when they reach the surface of theoilwhere they ignite explosively as soon as they come in 'contactwithvthe oxygen of the air. It is also probable that the air at thesurface of the oil is impregnated with oil vapor, and forms an explosivemixture which is ignited by the hot vapors from the arc. The variousplans proposed for inclosing the are or ,limiting its direct action uponthe oil have but little effect in preventing explosions due to the hotbubbles of vapor rising into the air space from the oil.

The-object of my invention is to prevent Specification of LettersPatent.

Patented Apr. 25, 1916.

Application filed October 11, 1912. Serial No. 725,172.

explosions of every kind in oil switches, even when the switches opencircuits carrying very large amounts of energy. I accomplish the desiredresult by not only dampening and diminishing the direct explosive actionof the arc, but also by preventing the access of hot vapor or partlclesto the air space above the surface of theoil. To this end, I providemeans for so reducing the temperature of the vapor and particles fromthe are, that by the time they reach the surface of the oil they are atsuch a'low temperature that they will not cause explosions.

-My invention will best be understood by reference to the accompanyingdrawing, in which I have shown merely for purposes of illustration, oneof the many forms in which the invention may be embodied, and in isprovided with a suitable cover, in which there is mounted an insulatorfor carrying a stationary contact I) submerged in the oil in the tank. Acooperating movable contact 0 is mounted to move vertically into and outof engagement with the stationary contact and to move toward the bottomof the tank as the circuit is opened. 7

The are formed upon the separation of the contacts 6 and 0tends'to'expand and throw the oil away from the contacts, and thisaction of the arc may be suflicient to throw the oil out of the tank. Toprevent this direct explosive action of the are, and also to preventaccess of the hot arc vapors and particles to the air space above theoil, I surround the contacts with some good heat conducting shell, whichis preferably metallic andhas many perforations,so that thehot gases ofthe expanding arc must pass through this perforated v metal shell. Owingto the small perforations? and the inertia and viscosity of the oil inthem, the arc encounters a great deal of resistance as it attempts toexpand through the metal shell. In this way the direct explosive efiectof the arc is weakened. The are gases are furthermore sub-divided intomany small jets and are very much cooled by passing through the metalshell. As

the perforated protecting these small jets enter the body of oil in thetank they are further cooled until any are gases or vapor bubbles whichreach the surface of the oil are at such a low temperature that noignition or explosion can occur.

One particular form ofheat conducting shell which I may use, isindicated in the drawing, which shows the contacts surrounded by aprotecting shell or barrier d consisting of a series of parallel flatrings made of some suitable metal, such as copper. These copper ringsare bent up slightly at their outer edge, and are spaced away from eachother to a slight extent to leave between them, comparatively smallpassages through which the arc gases may pass out into the body of oilin the tank. The copper rings are insulated from one another in anysuitable way, as by insulating spacers,"and are firmly held in properrelation to the contacts and to each other by bolts which extend thrpughthe plates. By insulating the individual parts or rings of body (Z, theare formed when the circuit is opened cannot use the protecting body 03as a metallic bridge between the two contacts, but instead theprotecting body breaks the arc up into a number of small arcs in series,which are more easily extinguished by the oil than one continuous arc ofequal length.

As the contacts separate, the are formed between them tends to expandand the hot arc gases are driven out through the passages between themetal rings. As these passages are narrow and are scaled up with oil,

' the protecting body of acts to some extent like an inclosing chamberfor the arc and very materially decreases the direct explosive action ofthe arc. The metal rlngs abstract a great deal of heat f'romthe arcgases flowing between them, and also compel the arc gases to emerge fromthe protecting shell in the form of thin sheets instead of in acompactbody. The oil in the tank exerts a much more marked cooling andextinguishing action upon the gases in the form of thin sheets than itwould upon an equal amount of gas in a compact mass or bubble.

In the particular switch shown in the drawing, the protecting shell dextends downwardly nearly to a point that corresponds to the lowestposition of the movable contact 0. 'In case there is any danger that thearc gases may be driven out of the lower end of the protecting shell 0!and then rise 'to the surface of the ,oil without suflicient cooling,the protecting shell may be made longer. In order to guard still furtheragainst the access of hot gases and heated particles to the airspaceabove the oil, protecting bodies of good heat conductlng material andprovided with many perforations may be placed above the contacts ordirectly at the surface of the oil. For example, a perforated protectingbody 6 may be placed above the protecting body (Z in any suitableposition, which may be on the surface of the oil, or directly under orover it. The protecting body 6 may be made in any suitable manner,preferably of a thick perforated metal plate.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. An electric switch comprising an oil vessel, relatively movablecooperating contacts mounted toseparate beneath the oil in said vessel,means for moving one of said contacts vertically away from the other toopen the circuit, and a protecting bell shaped shell with a closed topand open at the bottom and mounted beneath the oil in said vessel withthe open end down and with the upper one of saidcontacts alwa s Withinsaid bell and near the upper c osed end thereof, said protecting shellhaving in its walls restricted vents ,to permit only slow escape of arcgases and to cool said escaping gases.

2. An electric switch comprising an oil vessel, a fixed contact mountedin said vessel beneath the oil, a cooperating movable 00111351013mounted to move downwardly from said fixed contact to open the circuit,and aprotecting bell shaped shell closed at the top and open at thebottom and secured to sages to cool the escaping arc gases, and avertically movable cooperating contact separable from said fixed contactwithin said bell to draw an are within said bell and be: neath theimperforate top ofsaid bell and thus compel the arc gases formed within.said bell to pass through said narrow passages,

In witness whereof, I have hereunto set myhand this eighteenth dayof-September, 1912.

RICHARD TRfjGER.

Witnesses:

- JULIUs RUMLANDS,

ALFRED WOLF.

